/*
 * Copyright 2014 The Netty Project
 *
 * The Netty Project licenses this file to you under the Apache License,
 * version 2.0 (the "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at:
 *
 *   http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
 * License for the specific language governing permissions and limitations
 * under the License.
 */
package io.netty.channel.epoll;

import io.netty.channel.Channel;
import io.netty.channel.ChannelException;
import io.netty.channel.socket.ServerSocketChannel;
import io.netty.channel.socket.SocketChannel;
import io.netty.channel.unix.FileDescriptor;
import io.netty.channel.unix.Socket;
import io.netty.util.concurrent.GlobalEventExecutor;
import io.netty.util.internal.PlatformDependent;

import java.io.IOException;
import java.net.InetAddress;
import java.net.InetSocketAddress;
import java.net.SocketAddress;
import java.net.UnknownHostException;
import java.nio.channels.AlreadyConnectedException;
import java.util.Collection;
import java.util.Collections;
import java.util.Map;
import java.util.concurrent.Executor;

import static io.netty.channel.unix.Socket.newSocketStream;

/**
 * {@link SocketChannel} implementation that uses linux EPOLL Edge-Triggered
 * Mode for maximal performance.
 */
public final class EpollSocketChannel extends AbstractEpollStreamChannel
        implements SocketChannel
{

    private final EpollSocketChannelConfig config;

    private volatile InetSocketAddress local;

    private volatile InetSocketAddress remote;

    private InetSocketAddress requestedRemote;

    private volatile Collection<InetAddress> tcpMd5SigAddresses = Collections
            .emptyList();

    EpollSocketChannel(Channel parent, Socket fd, InetSocketAddress remote)
    {
        super(parent, fd);
        config = new EpollSocketChannelConfig(this);
        // Directly cache the remote and local addresses
        // See https://github.com/netty/netty/issues/2359
        this.remote = remote;
        local = fd.localAddress();

        if (parent instanceof EpollServerSocketChannel)
        {
            tcpMd5SigAddresses = ((EpollServerSocketChannel) parent)
                    .tcpMd5SigAddresses();
        }
    }

    public EpollSocketChannel()
    {
        super(newSocketStream(), false);
        config = new EpollSocketChannelConfig(this);
    }

    /**
     * @deprecated Use {@link #EpollSocketChannel(Socket, boolean)}.
     */
    @Deprecated
    public EpollSocketChannel(FileDescriptor fd)
    {
        super(fd);
        // As we create an EpollSocketChannel from a FileDescriptor we should
        // try to obtain the remote and local
        // address from it. This is needed as the FileDescriptor may be
        // bound/connected already.
        remote = fd().remoteAddress();
        local = fd().localAddress();
        config = new EpollSocketChannelConfig(this);
    }

    /**
     * Creates a new {@link EpollSocketChannel} from an existing
     * {@link FileDescriptor}.
     */
    public EpollSocketChannel(Socket fd, boolean active)
    {
        super(fd, active);
        // As we create an EpollSocketChannel from a FileDescriptor we should
        // try to obtain the remote and local
        // address from it. This is needed as the FileDescriptor may be
        // bound/connected already.
        remote = fd.remoteAddress();
        local = fd.localAddress();
        config = new EpollSocketChannelConfig(this);
    }

    /**
     * Returns the {@code TCP_INFO} for the current socket. See
     * <a href="http://linux.die.net/man/7/tcp">man 7 tcp</a>.
     */
    public EpollTcpInfo tcpInfo()
    {
        return tcpInfo(new EpollTcpInfo());
    }

    /**
     * Updates and returns the {@code TCP_INFO} for the current socket. See
     * <a href="http://linux.die.net/man/7/tcp">man 7 tcp</a>.
     */
    public EpollTcpInfo tcpInfo(EpollTcpInfo info)
    {
        try
        {
            Native.tcpInfo(fd().intValue(), info);
            return info;
        }
        catch (IOException e)
        {
            throw new ChannelException(e);
        }
    }

    @Override
    public InetSocketAddress remoteAddress()
    {
        return (InetSocketAddress) super.remoteAddress();
    }

    @Override
    public InetSocketAddress localAddress()
    {
        return (InetSocketAddress) super.localAddress();
    }

    @Override
    protected SocketAddress localAddress0()
    {
        return local;
    }

    @Override
    protected SocketAddress remoteAddress0()
    {
        return remote;
    }

    @Override
    protected void doBind(SocketAddress local) throws Exception
    {
        InetSocketAddress localAddress = (InetSocketAddress) local;
        fd().bind(localAddress);
        this.local = fd().localAddress();
    }

    @Override
    public EpollSocketChannelConfig config()
    {
        return config;
    }

    @Override
    public ServerSocketChannel parent()
    {
        return (ServerSocketChannel) super.parent();
    }

    @Override
    protected AbstractEpollUnsafe newUnsafe()
    {
        return new EpollSocketChannelUnsafe();
    }

    private static InetSocketAddress computeRemoteAddr(
            InetSocketAddress remoteAddr, InetSocketAddress osRemoteAddr)
    {
        if (osRemoteAddr != null)
        {
            if (PlatformDependent.javaVersion() >= 7)
            {
                try
                {
                    // Only try to construct a new InetSocketAddress if we using
                    // java >= 7 as getHostString() does not
                    // exists in earlier releases and so the retrieval of the
                    // hostname could block the EventLoop if a
                    // reverse lookup would be needed.
                    return new InetSocketAddress(
                            InetAddress.getByAddress(remoteAddr.getHostString(),
                                    osRemoteAddr.getAddress().getAddress()),
                            osRemoteAddr.getPort());
                }
                catch (UnknownHostException ignore)
                {
                    // Should never happen but fallback to osRemoteAddr anyway.
                }
            }
            return osRemoteAddr;
        }
        return remoteAddr;
    }

    @Override
    protected boolean doConnect(SocketAddress remoteAddress,
            SocketAddress localAddress) throws Exception
    {
        if (localAddress != null)
        {
            checkResolvable((InetSocketAddress) localAddress);
        }
        InetSocketAddress remoteAddr = (InetSocketAddress) remoteAddress;
        checkResolvable(remoteAddr);

        if (remote != null)
        {
            // Check if already connected before trying to connect. This is
            // needed as connect(...) will not return -1
            // and set errno to EISCONN if a previous connect(...) attempt was
            // setting errno to EINPROGRESS and finished
            // later.
            throw new AlreadyConnectedException();
        }

        boolean connected = super.doConnect(remoteAddress, localAddress);
        if (connected)
        {
            remote = computeRemoteAddr(remoteAddr, fd().remoteAddress());
        }
        else
        {
            // Store for later usage in doFinishConnect()
            requestedRemote = remoteAddr;
        }
        // We always need to set the localAddress even if not connected yet as
        // the bind already took place.
        //
        // See https://github.com/netty/netty/issues/3463
        local = fd().localAddress();
        return connected;
    }

    private final class EpollSocketChannelUnsafe extends EpollStreamUnsafe
    {
        @Override
        protected Executor prepareToClose()
        {
            try
            {
                // Check isOpen() first as otherwise it will throw a
                // RuntimeException
                // when call getSoLinger() as the fd is not valid anymore.
                if (isOpen() && config().getSoLinger() > 0)
                {
                    // We need to cancel this key of the channel so we may not
                    // end up in a eventloop spin
                    // because we try to read or write until the actual close
                    // happens which may be later due
                    // SO_LINGER handling.
                    // See https://github.com/netty/netty/issues/4449
                    ((EpollEventLoop) eventLoop())
                            .remove(EpollSocketChannel.this);
                    return GlobalEventExecutor.INSTANCE;
                }
            }
            catch (Throwable ignore)
            {
                // Ignore the error as the underlying channel may be closed in
                // the meantime and so
                // getSoLinger() may produce an exception. In this case we just
                // return null.
                // See https://github.com/netty/netty/issues/4449
            }
            return null;
        }

        @Override
        boolean doFinishConnect() throws Exception
        {
            if (super.doFinishConnect())
            {
                remote = computeRemoteAddr(requestedRemote,
                        fd().remoteAddress());
                requestedRemote = null;
                return true;
            }
            return false;
        }
    }

    void setTcpMd5Sig(Map<InetAddress, byte[]> keys) throws IOException
    {
        this.tcpMd5SigAddresses = TcpMd5Util.newTcpMd5Sigs(this,
                tcpMd5SigAddresses, keys);
    }
}
